The bending of light, also known as refraction, occurs due to the change in the speed of light as it passes from one medium to another. When light travels from a rarer medium (such as air) to a denser medium (such as water or glass), it slows down. This change in speed causes the light to bend or refract.

The amount of bending depends on the difference in the refractive indices of the two media. The refractive index of a medium is a measure of how much light bends when passing through it. The higher the refractive index, the more the light bends.

The formula for the angle of refraction is:

```

sin(angle of incidence) / sin(angle of refraction) = n2 / n1

```

where:

* angle of incidence is the angle between the incident light ray and the normal to the surface of the medium

* angle of refraction is the angle between the refracted light ray and the normal to the surface of the medium

* n1 is the refractive index of the first medium

* n2 is the refractive index of the second medium

The bending of light is a fundamental property of light waves and has many applications in optics, such as in the design of lenses and prisms.